Process and apparatus for separating articles

ABSTRACT

Process and device for separating potatoes from impurities such as clods and stones. The process consists of contacting the items to be examined by a pair of spaced feelers which are connected with a measuring device for determining capacity and ohmic conductivity of the items being tested. Various mechanical arrangements are provided for sequentially presenting test articles and for mechanically sorting or distributing the test articles responsive to the test results.

United States Patent Peter Albert Martini Naupliastrasee 7, Munich, Germany 780,924

Oct. 10, 1968 May 11, 1971 Inventor Appl. No. Filed Patented PROCESS AND APPARATUS FOR SEPARATING ARTICLES 10 Claims, 8 Drawing Figs.

US. Cl. 209/81, 1 324/71, 209/74 Int. Cl B07c 5/344 FieldofSearch 209/81,75;

324/71 (NEP), 73, 61 (NEP),61 (inquired) References Cited UNITED STATES PATENTS 2,362,691 11/1944 Gaiser 209/81 2,467,773 4/ 1949 Parker 209/8 1 3,200,888 8/1965 Lehde et al. 209/ 8 1 X 3,268,073 8/1966 Lehde et al. 209/81X 3,286,811 11/ 1966 McWilliams 198/155X Primary Examiner-Allen N. Knowles AttorneyFleit, Gipple & Jacobson OSCILLATOR ,3

I I J; J.-

, 2 Sheets-Sheet 1 PETER" A, MARTINI I INVENTOR Patentea fMay 11 a 3,578,160

2 Sheets-Sheet 2 PETER A.1MART|-:

INVENTOR F/'a.a

ORNIiYS PROCESS AND APPARATUS FOR SEPARA'I'ING ARTICLES The present invention relates to a process and a device for separating stones, clods and the like from root crops, especially potatoes, and also for separating rotten and damaged potatoes from good potatoes and is preferably but notexclusively intended for use as an attachment to a harvesting machine.

When lifting root crops, such as potatoes, by means of a harvesting machine, mechanical separating is customarily employed in the form of a variety of devices, utilizing as operative criteria one or more of the following physical properties: specific weight, fonn, rolling capacity. But the effectiveness of such sorting devices has proven to be no more than 90 percent.

Accordingly, the art has sought better methods hoping to obtain increased efficiency. Electricity was used, and'sorting has been tried using the different ohmic conductivity of the items being processed (potatoes, stones, clods). By this method, the potato peels had to be damaged by needles, knives, or discs, because one requisite was that the sensing implement touch the interior of the potatoes, which region of the potato is well known to be of good conduction. This piercing or bruising of the potato caused subsequent rotting.

The art has also proposed that the potatoes and the other items being processed (Impurities, for instance, clods) be transported, one by one, through a passage, for instance, a channel of plastics, where they would pass between two electrodes arranged in an appropriate position, for instance, beneath or above the passage. The object of this arrangement is to measure changes in capacity in the space between the electrodes. Unfortunately, this proposal was not very successful because wet clods or rotten or damaged potatoes could not be distinguished with certainty from good potatoes.

The object of this invention is to provide a process and apparatus which solves the described difficulty or problem by providing a technical solution which involves the simultaneous measuring of capacity and ohmic conductivity, and the sorting in dependence upon the result of the measurements.

Other and further objects and advantages of the invention will become readily apparent from the following detailed description of preferred embodiments of the inventive concept when taken in conjunction with the apending drawings in which:

FIG. 1 portrays schematically a potato undergoing test;

FIG. 2 is the equivalent circuit of the arrangement shown in FIG. 1;

FIG. 3 is an equivalent test circuit;

FIG. 4 is an equivalent for schematical test circuit according to the principles of the invention;

FIGS. 5 and 6 show alternative test arrangements;

FIG. 7 illustrates schematically a preferred form of the conveyor for testing configuration; and

FIG. 8 shows schematically the conveyor arrangement for transporting potatoes through the test and sorting cycle.

The working of the process is described as follows. The potato peel shows generally no conductivity, but the interior of the potato is a relatively good conductor. If, according to FIG. 1, two electrodes 30 and 3b are contacted with peel 2 of potato I, the equivalent circuit diagram of FIG. 2 results, with the capacities 4a and 4b formed by the peel, and the resistance 5 formed by the interior of the potato. The condenser 6 represents the stray capacity of the electrodes. It amounts to about l-Z LF.

Where, according to the invention, both electrodes touch a succession of test objects (objects of measurement) at points with a preselected spacing, similar values (dates) of the components 4a, 4b, 5 and 6 will result-in spite of various sizes of the test objects (objects of measurements). For nonconducting materials, like stones or dry clods, the value of the capacity measurable between the electrodes 3 increases to about 2-3 uuF, whereas at a measuring frequency of 5 MegaHertz or Mc/sec. a potato between the electrodes (e.g., lying on or under) produces a resulting capacity of 5l0 .LuF. or picofarad. A simple process for measuring the capacity is by measuring the alternating current conductivity.

As described in FIG. 3, a one side grounded oscillator 7 with output amplitude U is connected to the electrode 3a, whereas the electrode 3b is connected to ground via a resistance 8. The higher the capacity is between 3a and 3b, the higher is the voltage U, across the resistance 8. Stones and clods can, therefore, be distinguished with'security from potatoes'by measuring the alternating current resistance between the electrodes. Wet clods, however, show an ohmic conductivity, which, likewise, produces a voltage U,, correspondingly higher as the conductivity of the clod is higher. According to the invention, the preferred circuit arrangement is as shown in FIG. 4. Besides the alternating current source (oscillator 7), a direct current source 9 is provided. They are isolated from each other by condenser 10 and resistor 11. Items 11 and 13 are resistors.

Utilizing the inventive arrangement of FIG. 4, if a test object (object of measurement) without ohmic conductivity (potato,

stone, dry clod) touches the electrodes 3a, 3b, the increasing of capacity causes, as already described, an increasing of the alternating current output voltage U,.

If, however, the test object (object of measurement) has an ohmic conductivity it operates like an ohmic resistance 21 and, there results, besides an alternating current output voltage U,, also a direct current output voltage U at the condenser 14. The condenser 12 and resistor 13 serve to decouple direct current and alternating current voltages U, and U If an alternating current voltage exists, which is higher than a given threshold voltage, and if, at the same time, nearly no direct voltage U, can be measured, this confinns that the test object (object of measurement) is a potato. If a noticeable alternating current voltage U, appears and, at the same time, a direct current voltage exists which lies over a direct current threshold voltage U the test object (object of measurement) is a wet (moist, damp) clod or a very wet stone. By choosing fitting threshold voltages, potatoes with outside wet peels, which, therefore, have a thin high ohmic water film, can be easily distinguished from the much better conducting clods.

The alternating current voltage U, can be rectified and amplified. After amplifying the direct current voltage U both voltages can be conducted to a conventional switching device which controls a conventional mechanical sorting apparatus and thereby good potatoes, stones, clods, and rotten and damaged potatoes can be sorted out.

Point contact between electrodes and test object (object of measurement) may be made in a simple way. The electrodes, according to FIG. 5, can be two parallel bars 15 and 16 which are arranged in a distance of 1-4 cm. and on which the test object (object of measurement) is lying or on which it is- -preferably in longitudinal direction of the barsgliding or rolling. Further devices are possible, such as two spring wire bows l8 and 19or other contact pieces (feelerlike devices)- -which are adapted to glide over the test object (object of measurement) while it is carried on an isolated support 20. The feelers (contact pieces) and/or the support (base plate) may be movably arranged.

There may also be holes like in a gaming box which expand and let the object fall through, if the desired test is given.

The measuring device may be fon'ned as a little case, like a transistor radio, but with plugs, so that it may easily be interchanged by the farmer.

A plurality of measuring stations may be connected in a shunt arrangement (parallel connection) with a single alternating and a single direct current source.

The mechanical sorting may-controlled by the measuring apparatus-be made by switches, flaps, traps, lids, etc., which function to lead good potatoes and impurities (stones, clods, rotten and damaged potatoes) different ways, or by other mechanical fittings or other devices, as, for instance, buffers or the like, which are, e.g., constantly in action (for instance, by mechanical means, electric power or pneumatic means (compressed air), and which expel stones, clods and poor (unfit) potatoes and are only stopped if a good (fit) potato passes. it is technically also possible to expel the good potatoes, for instance, into a container, but it is better to treat the good potatoes carefully and to expel the impurities.

The device may also be used for the sorting of rotten and damaged potatoes from a potato bin, for example, in a store and also for the sorting of rotten apples and other fruits which have a rather isolating peel. (As the device discerns the peel, it is easy to sort out the rotten and damaged potatoes or fruits if they come to touch the electrodes with the rotten or damaged side. To make the sorting perfect, the device may be provided with mechanical means to turn the test objects, or several pairs of feelers can be provided at different attitudes.)

There now follows a description of a mechanical structure which can function responsive to the measuring device to effect the actual sorting. Each test piece must be transported, after being singled out, to the test point (measuring point) at which the relative position of the test pieces to the measuring instruments should be fixed as accurately as possible. The sorting device must work independently of weight and size of the pieces to be sorted; it ought to be sturdy and should not need much electrical or other control energy. Furthermore, according to the required sorting capacity, several of the cited sorting devices must be connectable in parallel. One single device will be able to sort about 2-5 single objects per second. And, last but not least, the disturbances which earth and other admixtures (impurities) cause must be avoided as efficiently as possible. At ordinary switches, mountains of soil are formed so that an extra man would be needed, and the scope of saving manpower and therewith the scope of the whole machine would become illusory.

According to the invention these requirements are fulfilled by using preferably ring-formed (bow-, circle-fonned) and lowerable (switchable) transport devices 22. The transport devices 22 consist of a ring and upright retainer with a nose 23 which is slidingly received in a guide rail 24, and legs 32 fixed to ferrules 33 pivotally mounted on cable 25. The devices 22 are moved by cable 25, which can be a steel cable. After having passed a supply container, where each ring is supplied preferably with only one object (potato, or stone, or clod, and so on), the cable 25 with the rings 22 is transported slidingly along U-formed rail 24 and past test feelers 26 (measuring feelers) electrically connected to measuring device 27.

If the measuring device 27 confirms that the object under test is a potato, it actuates a mechanism which, in turn, actuate the switch 28 in the U-formed conducting rail 24 and causes switch 28 to open so that the nose 23 of ring 22 is released and, hence, ring 22 will turn to the side or drop down, and the potato carried by ring 22 will fall upon a conveyor band 29 or the like running normal to cable 25. By the turning (or dropping) of the ring, the switch (sideway) may close itself in any conventional way, such as by a solenoid responsively actuated.

With the switch 28 remaining closed, stones, clods, unfit potatoes, or empty rings (bows) pass the test point, and all impurities or foreign bodies fall on a second conveyor 30 or back onto the ground (field). Alternatively, the operation of switch 28 may be reversed, and the switch opens for stones, clods, and so on and remains closed for good potatoes.

The measuring device may have two feelers. It may also work with one feeler alone if the ring 22, which is connected in a conducting way with the steel cable 25, serves as a counand the impurities which fall thereon are gravity fed to a discharge point which could be a dump or even another conveyor.

It would be useful to sort the items beforehand according to size, so that they fit the rings which may be of different size according to the size of the organ pipelike leading channels.

l claim: I 1. Method of controlling a device for sorting the components of a mixture of potatoes and foreign substancesutilizing the different electric properties of the potatoes and foreign substances, comprising moving the mixture along a path of movement having a plurality of electrodes arranged therewith; applying a direct current and an alternating current to the mixture through at least one of the said electrodes;

measuring simultaneously the direct current conductivity and the alternating current conductivity of the mixture and controlling the sorting of the mixture according to the proportion between the two measured values of individual components of the mixture.

2. Apparatus for controlling a device for sorting components of a mixture of potatoes and foreign substances by the utilization of different electrical properties of the potatoes and foreign substances comprising two electrodes arranged in the path of conveyance of the mixture, said electrodes being connected to both a source of alternating current and a source of direct current and being connected to means for simultaneously measuring the alternating current and the direct current conductivity of the components of the mixture, said measuring means controlling the device for sorting the components of the mixture.

3. Apparatus according to claim 2, wherein a source of direct voltage and a source of alternating voltage are connected to one of the electrodes and a direct current measuring instrument and an alternating current measuring instrument are connected to the other electrode.

4. Apparatus according to claim 3, wherein the source of alternating voltage is an oscillator and source of direct voltage is a battery, said sources being connected in parallel to one of the electrodes.

5. Apparatus according to claim 2, wherein several pairs of electrodes are connected to the alternating current source, as well as to the direct current source.

6. Apparatus according to claim 2, wherein the electrodes are parallel bars which contact the object to be measured.

7. Apparatus according to claim 6, wherein the object to be measured is contacted in the longitudinal direction of the electrodes.

8. Apparatus according to claim 2, wherein the electrodes are feelers which feel the components of the mixture.

9. Apparatus according to claim 2, wherein the electrodes are arranged in apertures on which the components of the mixture are conducted.

10. Apparatus according to claim 2, wherein it is a part of a potato harvesting machine. 

1. Method of controlling a device for sorting the components of a mixture of potatoes and foreign substances utilizing the different electric properties of the potatoes and foreign substances, comprising moving the mixture along a path of movement having a plurality of electrodes arranged therewith; applying a direct current and an alternating current to the mixture through at least one of the said electrodes; measuring simultaneously the direct current conductivity and the alternating current conductivity of the mixture and controlling the sorting of the mixture according to the proportion between the two measured values of individual components of the mixture.
 2. Apparatus for controlling a device for sorting components of a mixture of potatoes and foreign substances by the utilization of different electrical properties of the potatoes and foreign substances comprising two electrodes arranged in the path of conveyance of the mixture, said electrodes being connected to both a source of alternating current and a source of direct current and being connected to means for simultaneously measuring the alternating current and the direct current conductivity of the components of the mixture, said measuring means controlling the device for sorting the components of the mixture.
 3. Apparatus according to claim 2, wherein a source of direct voltage and a source of alternating voltage are connected to one of the electrodes and a direct current measuring instrument and an alternating current measuring instrument are connected to the other electrode.
 4. Apparatus according to claim 3, wherein the source of alternating voltage is an oscillator and source of direct voltage is a battery, said sources being connected in parallel to one of the electrodes.
 5. Apparatus according to claim 2, wherein several pairs of Electrodes are connected to the alternating current source, as well as to the direct current source.
 6. Apparatus according to claim 2, wherein the electrodes are parallel bars which contact the object to be measured.
 7. Apparatus according to claim 6, wherein the object to be measured is contacted in the longitudinal direction of the electrodes.
 8. Apparatus according to claim 2, wherein the electrodes are feelers which feel the components of the mixture.
 9. Apparatus according to claim 2, wherein the electrodes are arranged in apertures on which the components of the mixture are conducted.
 10. Apparatus according to claim 2, wherein it is a part of a potato harvesting machine. 